The Research On Mechanism And Device Of Aged Oil Demulsification Under High Voltage And High Frequency Pulsed AC Electric Field

The difficulty of aged oil treatment is a universal problem for oil fields.The main processing contains increasing settling time,improving the operating temperature or increasing demulsifier concentration which have limited effect and high energy consumption.But for offshore platforms,due to limited space and bearing,electric demulsification dehydration is clearly more appropriate with its widely use and mature technology.But the electric field of conventional electric dehydrator which has power frequency is easy to break down.Therefore,compact and efficient pipe electrostatic coalescence technology becomes one of the most optimal choice of aged oil on offshore platforms.Based on above consideration,this paper carries out the aging oil emulsion electric demulsification properties experimental study on the macroscopic and microscopic level and builds on that,develops structural design and performance test of round tube bundle runner compact electrostatic pipe coalescer.First of all,the deformation,coalescence and fracture behavior of single droplet and double droplets under high frequency/high voltage pusled AC electric field are studied with the use of high speed camera and polarized light microscope.The result shows that field strength has great influence on single droplet's deformation and double droplets' coalescence,and if field strength becomes too high,it will cause single drop to break and double drops uncontact.The frequency has little effect on the deformation of single droplet,but it can promote double droplets coalescence.The excessive frequency also lead to the break of double droplets coalescence.The above phenomenons can explain "electric dispersion" and the existence of optimal electric field parameters from micro level.Then the aged oil from Liuhua 11-1 oil field is used to conduct the electric demulsification and centrifugal dehydration static test.The experiment results show the existence of optimal voltage 1 k V/cm,frequency 2 k Hz,the optimal waveform is rectangular wave.The structure design and prototype machining of round tube bundle runner pipe electrocoalescer are carried out.The key structural part of electrocoalescer is high voltage insulating electrodes.The metal bare electrode with 0.6 mm thickness of FEP insulation layer is finalized.It is determined by the investigation of various insulation materials,processing methods and the breakdown voltage test of the electrodes with different thickness insulation layer.The result of electric field demulsification characteristic test shows that the optimal field strength is 1.44 k V/cm,the optimal frequency is 1.2 k Hz for water content of 30% emulsion,and the increasing duty ratio and decreasing flux rate are conductive to the electrostatic coalescence of water particles.It is proved the demulsification effectiveness of the round tube bundle runner pipe electrocoalescer under electric field.This study confirms the advantages of high frequency/high voltage pulsed AC electric field and electrostatic pipe coalescer from different levels,and provides data support and technical reference for optimization of aging oil treatment process in Liuhua 11-1 oil field.